Francis b



U ITED STATES PATENT OFFICE.

FRANCIS B. BADT, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE SIEMENS &

, HALSKE ELECTRIC COMPANY OF AMERICA, OF SAME PLACE:

ELECTRIC RHEOSTAT.

SPECIFICATION forming part of Letters Patent No. 544,278, dated. August13, 1895.

Application filed May 31, 1895. Serial No. 551,138. (No model.)

To aZZ whom it may concern:

Be it known that I, FRANCIS B. BADT, acitizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Rheostats, (Case No.55,) of

which the following is a full, clear, concise,-

and exact description, reference being bad to the accompanying drawings,forming a part of this specification.

My invention relates to a rheostat, and its object is to provide arheostat of noncombustible material in which the conductors carrying thecurrent may be thoroughly insulated, while the heat generated therebymay be readily radiated.

In accordance with my invention the resistance coils or conductors areembedded in a plate of glass, the glass being molded about the conductorin the formation of the glass. The glass plate is clamped between a pairof metal plates, preferably cast-iron, and ribbed to afford considerableradiating surface, a layer of yielding or elastic material beinginterposed between the glass and the metal plates whereby the expansionof the glass may be permitted.

I will describe my invention more in particular by reference to theaccompanying drawings, in which- Figure 1 is a plan View of a rheostatembodying my invention. Fig. 2 is a sectional view thereof on line 2 2,Fig. 1. Fig. 3 is a view of the rheostat with the upper radiating plateremoved, showing the position of the conductors within the glass plate.

Like letters refer to like parts in the several figures.

The resistance coils or conductors a a are embedded within the glassplate b, the'glass being molded about the conductors during theformation of the glass plate, whereby the conductors are completelyinclosed within the plate, and form a part of the same. The conductor isbrought from the end of the plate at intervals, whereby the contactterminals of the rh eostat may be electrically con nected with theconductors. I have illustrated the conductors as bent double and twistedupon themselves at the points where they extend from the edge of theplate, the

conductors being thus strengthened and atfording an increased carryingcapacity and an increased radiating-surface for the heat produced by thepassage of the currentthrough the conductors. The glass plate as thusformed is clamped between the metal plates 0 and d by means of bolts 6e. The plates are provided with ribs upon their outer faces, wherebyincreased radiating-surface is provided. One of the plates 0 is providedwith legs 0. c at its corners, through which screws 0 a? may be passedto screw the plate to the switchboard or other support. The plate 0 alsocarries a shelf or projection c 'adapted to bear the weight of the glassplate 1'). Between the glass plate and theradiating-plates c and d areinterposed layersfand gof yieldingor elastic material, adapted to permitthe expansion of the glass plate under the influence of heat. The layersfandg may be made of asbestos or sand, or any other yielding materialwhich will readily convey the heat from the glass to the metal plates.

The rheostat as thus constructed thoroughly insulates the electricalconductors, as they are formed integrally with and completely inclosedby the glass plate, and as glass is a fairly good conductor of heat, theheat generated in the conductors is readily conveyed through the glassplate to the metaliic radiating-plates, from the surfaces of which it isradiated. Furthermore, the materials of which the rheostat is made arenoncombustible, and danger from fire produced by the overheating of thecoils is thus avoided.

Having described my invention, what I claim as new, and desire to secureby Letters Patent, is

1. In a rheostat the combination with a glass plate, of electricalresistance conductors embedded in'said plate and extended from the plateat intervals for connection with the contact terminals of the rheostat,and metallic plates between which said glass plate is adapted to beclamped, and supported, substantially as described.

2. In a rheostat, the combination with a glass plate, of electricalconductors or resistance coils embedded or molded in said plate,metallic radiating plates upon the opposite sides of said glass plate,and a layer of yielding material interposed between said glass plate andeach of said' radiating plates, to permit the expansion of the glass;substantially as described.

3. In a rheostat, the combination with the glass plate I), of theelectrical conductors or resistance coils a a, embedded or molded!therein, the radiating plate a carrying the shelf 0 upon which saidglass plate is adapted to rest, radiating plate d between which and theradiating plate 0 said glass plate is FRANCIS B. BAD'I.

Witnesses:

CHARLES A. BROWN, W. CLYDE J ONES.

